1. Field of the Invention
This invention relates to a system for and a method of supplying ink to a stencil printer. This invention also relates to an ink container which is mounted on a stencil printer to supply ink to the stencil printer.
2. Description of the Related Art
There has been known a stencil printer in which print is made by the use of an image-wise perforated stencil. In such a stencil printer, a stencil is made by, for instance, bringing a thermal head having a plurality of heater elements arranged in a row or rows into contact with heat-sensitive stencil material with the heater elements selectively energized according to the image to be printed, thereby imagewise perforating the stencil material. The stencil thus made is wound around a printing drum and a printing paper is pressed against the stencil so that ink is transferred to the printing paper through the perforations. As a means for supplying ink to the stencil printer, there has been employed a mechanism comprising an ink supply roller which is supported for revolution about their respective axes by a pair of opposed plate, a distributor which supplies ink onto the ink supply roller and a doctor roller which is disposed spaced from the ink supply roller to control the thickness of ink film formed on the roller. As the distributor, those comprising a tubular member provided with a plurality of small holes or comprising a plurality of nozzles have been known. Ink in an ink container is sucked by an ink pump and is supplied onto the ink supply roller in the form of drops so that an ink fountain is formed in the wedge-like space between the ink supply roller and the doctor roller. Ink in the ink fountain is supplied into the printing drum through the gap between the ink supply roller and the doctor roller. A predetermined amount of ink is constantly held in the ink fountain so that ink can be uniformly supplied. That is, each time an ink sensor detects shortage of ink in the ink fountain, the ink pump is operated to replenish the ink fountain with ink. When the ink fountain is not replenished with ink after driving the ink pump for a predetermined time, the ink container is considered to be exhausted and the user is prompted to replace the ink container.
As the ink container employed in the stencil printer, there have been known, for instance, those comprising an outer box formed of corrugated board and a flexible inner bag accommodated in the outer box so that an ink discharge pipe formed on one end of the inner bag projecting outside the outer box with the outer end thereof closely sealed with a cap (will be referred to as “a BIC-type ink container”, hereinbelow) and those comprising a cylinder provided with an ink discharge port on the front thereof and a piston inserted into the cylinder (will be referred to as “a piston-type ink container”, hereinbelow). The latter piston-type ink container is advantageous over the former BIC-type ink container in that the amount of ink remaining in the ink container after ink is sucked to the very end is smaller and ink can be effectively used. In this ink container, an ink discharge port is formed on the front end of a small diameter portion and the ink container is sealed by a cap which is screwed on the ink discharge port. When using the ink container, the cap is unscrewed and the ink container is inserted into the stencil printer from the container holder of the stencil printer so that the ink suction port of the stencil printer is fitted with the small diameter portion of the ink container.
When the ink container is exhausted and ink therein comes not to be sucked out, the ink container must be replaced with a new ink container. When replacing the ink container, the vicinity of the ink suction port of the stencil printer can be stained with ink ejected from the ink container unless the ink container is carefully handled. The ink on the vicinity of the ink suction port of the stencil printer can stain the outer surface of the loaded ink container, and the ink on the outer surface of the loaded ink container can stain the user's hand in turn when the loaded ink container is exhausted and removed from the stencil printer.
Even an exhausted ink container is not completely free from ink but some ink remains near the ink discharge port. Further, since ink is sucked from the ink container through the ink suction port, the inside of the ink container and the ink suction port of the stencil printer is under vacuum. When the ink container is rapidly drawn out in this state, ink remaining around the junction of the ink container can be ejected out under the shock of drawing the ink container. This phenomenon is apt to occur in the piston-type ink containers and is less apt to occur in the BIC-type ink containers. It is believed that this is because ink remaining around the ink discharge port is returned inside the inner bag when the inner bag recovers its original shape in the case of the BIC-type ink containers whereas such effect cannot be expected in the case of the piston-type ink containers where the piston is substantially rigid.